Predaceous Insects and their Prey. 397 



a predaceous Dipterous larva of such special interest that 

 I determined to include it. 



Dr. T. A. Chapman (" Ent. Mo. Mag." 1905, pp. 150, 151 ; 

 1906, pp. 14-16) has observed the larva of Xanthandrus 

 comtus feeding upon Tortricid larvse, but only upon such 

 as are gregarious or at any rate numerous upon their food 

 plant. Hashda hyerana fulfilled this condition at Hyeres, 

 Acroclita consequana in Sicily, and a larva, probably of 

 Ancyhs derasana in the Alps : in all these cases Dr. Chap- 

 man found the larva of the Syrphid feeding upon that of the 

 Tortricid. In Sicily H. hyerana occurred singly, and the 

 Syrphid was not found attacking it. Dr. Chapman con- 

 cludes from these instances that " X. comtus feeds especially 

 on the larvse of Tortrices when there are many on a plant," 

 while " the isolation of the individual larvse " renders them 

 " an unsuitable prey for this parasite." The Syrphid larva 

 would in fact " perish when it had destroyed its solitary 

 prey and could find no others." 



It is of the highest interest therefore to establish the 

 fact, as Mr. G. T. Lyle of Brockenhurst has now done, that 

 the larva of this species is found attacking single Lepi- 

 dopterous larvse when they are large enough to provide 

 sufficient food. 



In August 1903 Mr. Lyle found the full-fed Syrphid 

 larva inside the shelter (constructed of sallow leaves 

 loosely spun together) of the larva of the Geometrid moth, 

 Scotosia undulata. Nothing remained of the latter except 

 the dry and empty skin. The Syrphid larva was of a 

 bright apple-green colour with darker markings. In 

 September 1903 the perfect insect emerged. The speci- 

 men, together with the empty globular puparium,* was 

 presented to the Hope Department by Mr. W. J. Lucas to 

 whom Mr. Lyle had given it. The fly, a male (309), was 

 kindly identified for me by Col. J. W. Yerbury. 



Putting together Dr. Chapman's and Mr. Lyle's 

 observations, there is reason for the opinion that the 

 female Syrphid is instinctively led to deposit her eggs 

 where there are either many minute larvse or single 

 larvse of sufficient size. The adaptation to two different 

 conditions under either of which sufficient food may be 

 provided is of much interest, and it is to be hoped that 

 further observations will be directed to the subject, so that 



* See Dr. T. A. Chapman's descrijjtion in "Ent. Mo. Mag." 1905, 

 p. 151. 



